summaryrefslogtreecommitdiff
path: root/cpukit/libfs/src/pipe/fifo.c
blob: 077d2770211dcaf6230f54d7b09e940e03867447 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
/**
 * @file
 *
 * @brief FIFO/Pipe Support
 * @ingroup FIFO_PIPE
 */

/*
 * Author: Wei Shen <cquark@gmail.com>
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.org/license/LICENSE.
 */


#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/param.h>
#include <sys/filio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include <rtems.h>
#include <rtems/libio_.h>
#include <rtems/pipe.h>

#define LIBIO_ACCMODE(_iop) (rtems_libio_iop_flags(_iop) & LIBIO_FLAGS_READ_WRITE)
#define LIBIO_NODELAY(_iop) rtems_libio_iop_is_no_delay(_iop)

static rtems_mutex pipe_mutex = RTEMS_MUTEX_INITIALIZER("Pipes");


#define PIPE_EMPTY(_pipe) (_pipe->Length == 0)
#define PIPE_FULL(_pipe)  (_pipe->Length == _pipe->Size)
#define PIPE_SPACE(_pipe) (_pipe->Size - _pipe->Length)
#define PIPE_WSTART(_pipe) ((_pipe->Start + _pipe->Length) % _pipe->Size)

#define PIPE_LOCK(_pipe) rtems_mutex_lock(&(_pipe)->Mutex)

#define PIPE_UNLOCK(_pipe) rtems_mutex_unlock(&(_pipe)->Mutex)

#define PIPE_READWAIT(_pipe)  \
  rtems_condition_variable_wait(&(_pipe)->readBarrier, &(_pipe)->Mutex)

#define PIPE_WRITEWAIT(_pipe)  \
  rtems_condition_variable_wait(&(_pipe)->writeBarrier, &(_pipe)->Mutex)

#define PIPE_WAKEUPREADERS(_pipe) \
  rtems_condition_variable_broadcast(&(_pipe)->readBarrier)

#define PIPE_WAKEUPWRITERS(_pipe) \
  rtems_condition_variable_broadcast(&(_pipe)->writeBarrier)

/*
 * Alloc pipe control structure, buffer, and resources.
 * Called with pipe_semaphore held.
 */
static int pipe_alloc(
  pipe_control_t **pipep
)
{
  static char c = 'a';
  pipe_control_t *pipe;
  int err = -ENOMEM;

  pipe = malloc(sizeof(pipe_control_t));
  if (pipe == NULL)
    return err;
  memset(pipe, 0, sizeof(pipe_control_t));

  pipe->Size = PIPE_BUF;
  pipe->Buffer = malloc(pipe->Size);
  if (pipe->Buffer == NULL) {
    free(pipe);
    return -ENOMEM;
  }

  rtems_condition_variable_init(&pipe->readBarrier, "Pipe Read");
  rtems_condition_variable_init(&pipe->writeBarrier, "Pipe Write");
  rtems_mutex_init(&pipe->Mutex, "Pipe");

  *pipep = pipe;
  if (c ++ == 'z')
    c = 'a';
  return 0;
}

/* Called with pipe_semaphore held. */
static inline void pipe_free(
  pipe_control_t *pipe
)
{
  rtems_condition_variable_destroy(&pipe->readBarrier);
  rtems_condition_variable_destroy(&pipe->writeBarrier);
  rtems_mutex_destroy(&pipe->Mutex);
  free(pipe->Buffer);
  free(pipe);
}

static void pipe_lock(void)
{
  rtems_mutex_lock(&pipe_mutex);
}

static void pipe_unlock(void)
{
  rtems_mutex_unlock(&pipe_mutex);
}

/*
 * If called with *pipep = NULL, pipe_new will call pipe_alloc to allocate a
 * pipe control structure and set *pipep to its address.
 * pipe is locked, when pipe_new returns with no error.
 */
static int pipe_new(
  pipe_control_t **pipep
)
{
  pipe_control_t *pipe;
  int err = 0;

  _Assert( pipep );
  pipe_lock();

  pipe = *pipep;
  if (pipe == NULL) {
    err = pipe_alloc(&pipe);
    if (err) {
      pipe_unlock();
      return err;
    }
  }

  PIPE_LOCK(pipe);

  *pipep = pipe;
  pipe_unlock();
  return err;
}

void pipe_release(
  pipe_control_t **pipep,
  rtems_libio_t *iop
)
{
  pipe_control_t *pipe = *pipep;
  uint32_t mode;

  pipe_lock();
  PIPE_LOCK(pipe);

  mode = LIBIO_ACCMODE(iop);
  if (mode & LIBIO_FLAGS_READ)
     pipe->Readers --;
  if (mode & LIBIO_FLAGS_WRITE)
     pipe->Writers --;

  PIPE_UNLOCK(pipe);

  if (pipe->Readers == 0 && pipe->Writers == 0) {
#if 0
    /* To delete an anonymous pipe file when all users closed it */
    if (pipe->Anonymous)
      delfile = TRUE;
#endif
    pipe_free(pipe);
    *pipep = NULL;
  }
  else if (pipe->Readers == 0 && mode != LIBIO_FLAGS_WRITE)
    /* Notify waiting Writers that all their partners left */
    PIPE_WAKEUPWRITERS(pipe);
  else if (pipe->Writers == 0 && mode != LIBIO_FLAGS_READ)
    PIPE_WAKEUPREADERS(pipe);

  pipe_unlock();

#if 0
  if (! delfile)
    return;
  if (iop->pathinfo.ops->unlink_h == NULL)
    return;

  /* This is safe for IMFS, but how about other FSes? */
  rtems_libio_iop_flags_clear( iop, LIBIO_FLAGS_OPEN );
  if(iop->pathinfo.ops->unlink_h(&iop->pathinfo))
    return;
#endif

}

int fifo_open(
  pipe_control_t **pipep,
  rtems_libio_t *iop
)
{
  pipe_control_t *pipe;
  unsigned int prevCounter;
  int err;

  err = pipe_new(pipep);
  if (err)
    return err;
  pipe = *pipep;

  switch (LIBIO_ACCMODE(iop)) {
    case LIBIO_FLAGS_READ:
      pipe->readerCounter ++;
      if (pipe->Readers ++ == 0)
        PIPE_WAKEUPWRITERS(pipe);

      if (pipe->Writers == 0) {
        /* Not an error */
        if (LIBIO_NODELAY(iop))
          break;

        prevCounter = pipe->writerCounter;
        err = -EINTR;
        /* Wait until a writer opens the pipe */
        do {
          PIPE_READWAIT(pipe);
        } while (prevCounter == pipe->writerCounter);
      }
      break;

    case LIBIO_FLAGS_WRITE:
      pipe->writerCounter ++;

      if (pipe->Writers ++ == 0)
        PIPE_WAKEUPREADERS(pipe);

      if (pipe->Readers == 0 && LIBIO_NODELAY(iop)) {
	PIPE_UNLOCK(pipe);
        err = -ENXIO;
        goto out_error;
      }

      if (pipe->Readers == 0) {
        prevCounter = pipe->readerCounter;
        err = -EINTR;
        do {
          PIPE_WRITEWAIT(pipe);
        } while (prevCounter == pipe->readerCounter);
      }
      break;

    case LIBIO_FLAGS_READ_WRITE:
      pipe->readerCounter ++;
      if (pipe->Readers ++ == 0)
        PIPE_WAKEUPWRITERS(pipe);
      pipe->writerCounter ++;
      if (pipe->Writers ++ == 0)
        PIPE_WAKEUPREADERS(pipe);
      break;
  }

  PIPE_UNLOCK(pipe);
  return 0;

out_error:
  pipe_release(pipep, iop);
  return err;
}

ssize_t pipe_read(
  pipe_control_t *pipe,
  void           *buffer,
  size_t          count,
  rtems_libio_t  *iop
)
{
  int chunk, chunk1, read = 0, ret = 0;

  PIPE_LOCK(pipe);

  while (PIPE_EMPTY(pipe)) {
    /* Not an error */
    if (pipe->Writers == 0)
      goto out_locked;

    if (LIBIO_NODELAY(iop)) {
      ret = -EAGAIN;
      goto out_locked;
    }

    /* Wait until pipe is no more empty or no writer exists */
    pipe->waitingReaders ++;
    PIPE_READWAIT(pipe);
    pipe->waitingReaders --;
  }

  /* Read chunk bytes */
  chunk = MIN(count - read,  pipe->Length);
  chunk1 = pipe->Size - pipe->Start;
  if (chunk > chunk1) {
    memcpy(buffer + read, pipe->Buffer + pipe->Start, chunk1);
    memcpy(buffer + read + chunk1, pipe->Buffer, chunk - chunk1);
  }
  else
    memcpy(buffer + read, pipe->Buffer + pipe->Start, chunk);

  pipe->Start += chunk;
  pipe->Start %= pipe->Size;
  pipe->Length -= chunk;
  /* For buffering optimization */
  if (PIPE_EMPTY(pipe))
    pipe->Start = 0;

  if (pipe->waitingWriters > 0)
    PIPE_WAKEUPWRITERS(pipe);
  read += chunk;

out_locked:
  PIPE_UNLOCK(pipe);

  if (read > 0)
    return read;
  return ret;
}

ssize_t pipe_write(
  pipe_control_t *pipe,
  const void     *buffer,
  size_t          count,
  rtems_libio_t  *iop
)
{
  int chunk, chunk1, written = 0, ret = 0;

  /* Write nothing */
  if (count == 0)
    return 0;

  PIPE_LOCK(pipe);

  if (pipe->Readers == 0) {
    ret = -EPIPE;
    goto out_locked;
  }

  /* Write of PIPE_BUF bytes or less shall not be interleaved */
  chunk = count <= pipe->Size ? count : 1;

  while (written < count) {
    while (PIPE_SPACE(pipe) < chunk) {
      if (LIBIO_NODELAY(iop)) {
        ret = -EAGAIN;
        goto out_locked;
      }

      /* Wait until there is chunk bytes space or no reader exists */
      pipe->waitingWriters ++;
      PIPE_WRITEWAIT(pipe);
      pipe->waitingWriters --;

      if (pipe->Readers == 0) {
        ret = -EPIPE;
        goto out_locked;
      }
    }

    chunk = MIN(count - written, PIPE_SPACE(pipe));
    chunk1 = pipe->Size - PIPE_WSTART(pipe);
    if (chunk > chunk1) {
      memcpy(pipe->Buffer + PIPE_WSTART(pipe), buffer + written, chunk1);
      memcpy(pipe->Buffer, buffer + written + chunk1, chunk - chunk1);
    }
    else
      memcpy(pipe->Buffer + PIPE_WSTART(pipe), buffer + written, chunk);

    pipe->Length += chunk;
    if (pipe->waitingReaders > 0)
      PIPE_WAKEUPREADERS(pipe);
    written += chunk;
    /* Write of more than PIPE_BUF bytes can be interleaved */
    chunk = 1;
  }

out_locked:
  PIPE_UNLOCK(pipe);

#ifdef RTEMS_POSIX_API
  /* Signal SIGPIPE */
  if (ret == -EPIPE)
    kill(getpid(), SIGPIPE);
#endif

  if (written > 0)
    return written;
  return ret;
}

int pipe_ioctl(
  pipe_control_t  *pipe,
  ioctl_command_t  cmd,
  void            *buffer,
  rtems_libio_t   *iop
)
{
  if (cmd == FIONREAD) {
    if (buffer == NULL)
      return -EFAULT;

    PIPE_LOCK(pipe);

    /* Return length of pipe */
    *(unsigned int *)buffer = pipe->Length;
    PIPE_UNLOCK(pipe);
    return 0;
  }

  return -EINVAL;
}